When did you last change your sauna stones?
It's the one bit of maintenance almost nobody is told about. Here's how often to do it, how to tell when it's time, and why it matters more than you'd think.
Crumbled stones, burnt-out elements.
This is something I see far too often in saunas around New Zealand, especially public ones. The stones in this heater probably hadn't been changed in years.
They'd crumbled, blocked the airflow, and the heating elements had completely burnt out. And it wasn't the first time: the elements had been replaced before, but nobody thought to change the stones at the same time.
Use it regularly? Change them once a year.
That's my rule of thumb. Beyond that, it depends on how often you use the sauna, the type of heater and the quality of the stones.
These are general guidelines, not official intervals for every heater brand. A public sauna at a gym or pool gets far more use than a home sauna, so it needs a very different schedule.
| Sauna used | Change the stones |
|---|---|
| 1–2 times a week | Every year |
| 3–5 times a week | At least once a year |
| Every day | Every 6–12 months |
| Public sauna in constant use | Possibly every few months, depending on use and condition |
How do you know?
- They're crumblingStones are cracking or breaking apart.
- Bits at the bottomPieces of stone piling up at the bottom of the heater.
- Elements showingThe stones have settled and the heating elements are visible.
- Flat löylyThe steam just isn't as good as it used to be.
- Changed colourOld stones look completely different from fresh ones.
Quick test: take two stones and whack them hard together. If they break, it's time for new ones. In the photo, a fresh stone sits next to an old one that split.
Give them a check-up.
Pull the stones right out at least once a year. Just stirring the top layer isn't enough. In a commercial sauna, check them more often.
Power off, cool down
Switch the heater off at the isolator or breaker and let it cool right down. Never handle hot stones.
Everything out
Take all the stones out, top down, and pop them in a bucket.
Sort and clean
Throw out any cracked or crumbling ones. Clean the elements and vacuum the bits out of the bottom of the heater.
Back in, swapped
If the rest look good, put them back with the order swapped: top stones to the bottom, bottom to the top. Keep them loose and follow your heater's manual.
Don't force stones between the elements or pack them tight. Airflow is what keeps your elements alive. And once the stones are worn out, replace them; don't just keep reshuffling.
New elements? New stones too.
Worn-out stones restrict the airflow, and that shortens the life of your heating elements. So if you're replacing the elements anyway, do the stones at the same time. Otherwise you'll be replacing the elements again sooner than you think.
What we found, photographed.
